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Thu, 10 Apr 2025 08:45:51 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id YTo2Ej+F92fxDQAAD6G6ig (envelope-from ); Thu, 10 Apr 2025 08:45:51 +0000 Date: Thu, 10 Apr 2025 10:45:49 +0200 From: Oscar Salvador To: Baolin Wang Cc: akpm@linux-foundation.org, willy@infradead.org, david@redhat.com, hannes@cmpxchg.org, 21cnbao@gmail.com, ryan.roberts@arm.com, ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: huge_memory: add folio_mark_accessed() when zapping file THP Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Action: no action X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 9B4C0C0002 X-Stat-Signature: q1ubqday8bb8m9qb1n4mwtc44d14pjbc X-Rspam-User: X-HE-Tag: 1744274754-882887 X-HE-Meta: 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 H//rNEWI /gg59Ho9YlX/if1cx8aC0yVJw9nIKGe5knHedug+hsmpF9ltBgaqXmatkPeVbO02wVaXBt1QU+81gtH7O+jTYueaabcWFxHzqzQvSJqt2zLuV18vMM4vLRTp+tf5w9iYDLupWLF3Fs7GHUCcNiKfy41ekt3Xbh4XAZWk6pouh09fNQtiWKK4fh178firDH+FD+IwlHG5aNcMV2unK9gsbdDYP1FYCNFZBs70vFb2D5LkY+gpgGhF75loxLf3MQfZPOV2egHdcuhuQc1KQgCLme9t32XuRuXS8CNL5iwtaZVS4oJdXOzW29mZCYuXcAJdHx3s3XrhBRtVgz6YtjzHKfHIGrTfgcWI/LBvwSQrjIq2V0wgTgNuIAySTJg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000017, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Apr 09, 2025 at 05:38:58PM +0800, Baolin Wang wrote: > When investigating performance issues during file folio unmap, I noticed some > behavioral differences in handling non-PMD-sized folios and PMD-sized folios. > For non-PMD-sized file folios, it will call folio_mark_accessed() to mark the > folio as having seen activity, but this is not done for PMD-sized folios. > > This might not cause obvious issues, but a potential problem could be that, > it might lead to reclaim hot file folios under memory pressure, as quoted > from Johannes: > > " > Sometimes file contents are only accessed through relatively short-lived > mappings. But they can nevertheless be accessed a lot and be hot. It's > important to not lose that information on unmap, and end up kicking out a > frequently used cache page. > " > > Therefore, we should also add folio_mark_accessed() for PMD-sized file > folios when unmapping. > > Signed-off-by: Baolin Wang > Acked-by: Johannes Weiner > Acked-by: Zi Yan Reviewed-by: Oscar Salvador Although I agree with David here that pmd_present would be more obvious than flush_needed. It was not obvious to be at first glance. -- Oscar Salvador SUSE Labs